It has become a very important diagnosis and examination technique in the modem medical treatment by extending a very thin catheter and an endoscope into a patient's body via the patient's throat and using flash light and an image capture device to capture actual images of organ deep inside the patient's body. To enable convenient directional operation of image capturing, an endoscope device that uses lateral lighting to capture images has become an applied technique that has received wide attention of people. It is known the size of the endoscope has direct relation with the discomfort suffered by a patient when the endoscope invades the patient's throat, and the endoscope for use in industrial and other purposes must also have reduced size for extending into extremely small gaps to capture images. The endoscope would have largely limited applications if it could not have minimized dimensions. Therefore, it has become a critical technical point in designing the endoscope to miniaturize the size thereof.
In the currently available techniques, a side-viewing endoscope device for capturing images in a direction perpendicular to an axis of the endoscope is configured as a two-piece hollow capsule having a front and a rear capsule. The front capsule is provided on one side of its wall with a light window, and an inclined reflector is fixedly mounted in the front capsule corresponding to the light window, so that a laterally projected light source received by the reflector is refracted into an axial direction of the capsule. Further, the front capsule is provided around a rear open end with screw threads. The rear capsule has a front open end and is provided on a rear end with a through hole for a cable to extend therethrough. An optical camera lens, a light emitting element, and a cable are fixedly serially arranged to form a unit, which is extended into and fitted in the rear capsule. The optical camera lens faces toward the reflector, and the light emitting element emits light sidewardly relative to the axis of the capsule. The rear capsule is provided around the front open end with screw threads for meshing with the screw threads on the front capsule, so that the front capsule and the rear capsule are screwed to each other to complete the two-piece capsule for the conventional side-viewing endoscope. The side-viewing endoscope with the above-described configuration has the following disadvantages:
(1) In manufacturing the currently available side-viewing endoscope using threaded connection for its front and rear capsules, spaces allowing for forming screw threads of predetermined pitch and depth must be reserved on the endoscope. By doing this, it would prevent the endoscope from being further miniaturized. Further, with the miniaturized size of the endoscope, it is difficult or even impossible to align the front and the rear capsule with each other for screwing them together. Thus, the threaded connection is not a suitable design for the miniaturized side-viewing endoscope.
(2) In the unit consisting of the fixedly and serially arranged optical camera lens, light emitting element and cable, the optical camera lens actually has an outer diameter smaller than other elements and has to be mounted at the front open end of the rear capsule. Since the unit of the optical camera lens, light emitting element and cable must be disposed in the rear capsule via the front open end thereof with the optical camera lens located at the front open end, the front open end of the rear capsule would inevitably have an inner diameter larger than the outer diameter of the optical camera lens. Therefore, an additional locating means is required to hold the optical camera lens in place at the front open end of the rear capsule.